Field of the Invention
The present invention relates to a pilot-operated solenoid valve including a pilot valve unit having a fixed core and a movable core, and a passage block formed with a valve seat which a valve element comes into contact with or separates from.
Related Art
Heretofore, pilot-operated electromagnetic, or solenoid, valves for fluid control are used in for example general industrial machinery such as machine tools, welding machines, fusion cutting machines, transport machines, and air-conditioning equipment, medical machinery such as oxygen enrichers, or others. Some of conventional pilot-operated solenoid valves each include a diaphragm valve element as a main valve element and are configured to control the pressure of a back chamber of the diaphragm valve element by a solenoid valve to open and close the diaphragm valve element.
In a pilot-operated solenoid valve proposed in Patent Document 1, for example, when a first communication passage is to be communicated with a third communication passage, a pilot valve unit is operated to supply fluid to a back chamber of a diaphragm valve element, thereby pressurizing the back chamber, to bring the diaphragm valve element into contact with a valve seat. When the first communication passage is to be communicated with a second communication passage, the pilot valve unit is operated to communicate the back chamber of the diaphragm valve element with atmosphere, thereby discharging air from the back chamber to atmosphere in order to reduce the internal pressure of the back chamber. Thus, the diaphragm valve element is separated from the valve seat.
Further, there is a pilot-operated solenoid valve adaptable to both an external exhaust type configuration for discharging fluid from a back chamber of a diaphragm to atmosphere and an internal exhaust type configuration for discharging fluid from the back chamber of the diaphragm to an outlet port.